This invention relates to electronically controlled thermostats and in particular to the back up power capabilities of such thermostats during an outage of normal power.
Electronically controlled thermostats have heretofore included an emergency back up power capability that maintains a supply of power to essential operating components during power outage. This back up power has included use of either batteries or a supercapacitor capable of maintaining an appropriate voltage level for a limited period of time. This emergency back up has normally been provided to the microprocessor and associated memory within the thermostat. This provision of emergency power to the microprocessor and associated memory has however resulted in a significant drain on the emergency power source. This drain typically results in the emergency power running out in one hour or less. When this occurs, the thermostat needs to be manually reset including the resetting of a real time clock.